You can hold CTRL and click on multiple items on the taskbar, then right-click the last one to close them all. Very useful for quickly shutting all those folder windows you might have open. I find it invaluable now.

Actually, you can do more than close all of the selected Windows - once you've selected multiple items on the taskbar, right-click gives you the same set of options you get when you've enabled taskbar grouping, so you can also tile, cascade, and minimize the group. Handy.